300px|thumb|Lac tubes created by [[Kerria lacca]]
right|thumb|Resin secreted by the female lac bug on trees is processed and sold as dry flakes.
Lac is the resinous secretion of a number of species of lac insects, of which the most commonly cultivated is Kerria lacca.
Cultivation begins when a farmer gets a stick that contains eggs ready to hatch and ties it to the tree to be infested. Thousands of lac insects colonize the branches of the host trees and secrete the resinous pigment. The coated branches of the host trees are cut and harvested as sticklac.
The harvested sticklac is crushed and sieved to remove impurities. The sieved material is then repeatedly washed to remove insect parts and other material. The resulting product is known as seedlac. The prefix seed refers to its pellet shape. Seedlac, which still contains 3–5% impurity, is processed into shellac by heat treatment or solvent extraction.
The leading producer of lac is Jharkhand, followed by the Chhattisgarh, West Bengal, and Maharashtra states of India. Lac production is also found in Bangladesh, Myanmar, Thailand, Laos, Vietnam, parts of China, and Mexico.
Etymology
The word lac is derived from the Sanskrit word lākshā (लाक्षा) representing the number 100 thousand, which was used for both the lac insect (because of their enormous number) and the scarlet resinous secretion it produces that was used as wood finish, lacquerware, skin cosmetic, ornaments and dye for wool and silk in ancient India and neighbouring areas. Lac resin was once imported in sizeable quantity into Europe from India along with Eastern woods. These were being used very widely.
Host trees
thumb|upright|Pongam or honge ([[Millettia pinnata) is a native of India and grows in profusion, generally planted as avenue trees by the forest department. It is renowned for its shade and is well known in traditional uses for its medicinal properties. It is also grown as a host plant for lac insects. The tree is also one of the food plants for common cerulean (Jamides celeno).]]
Kerria lacca can be cultivated on either cultivated or wild host plants.
- In India the most common host plants are:
- Dhak (Butea monosperma)
- Ber (Ziziphus mauritiana)
- Kusum (Schleichera oleosa) (reported to give the best quality and yield)
- In Thailand the most common host plants are
- Rain tree (Albizia saman)
- Pigeon pea (Cajanus cajan)
- In China the common host plants include
- Pigeon pea (Cajanus cajan)
- Hibiscus species
- In Mexico
- Barbados nut (Jatropha curcas)
Estimated yields per tree in India are 6–10 kg for kusum, 1.5–6 kg for ber, and 1–4 kg for dhak.
Harvesting
Lac is harvested by cutting the tree branches that hold sticklac. If dye is being produced, the insects are kept in the sticklac because the dye colour comes from the insects rather than their resin. They may be killed by exposure to the sun. On the other hand, if seedlac or shellac is being produced, most insects can escape because less coloured pale lac is generally more desired. In China, it is a traditional dye for leather goods. Lac for dye has been somewhat replaced by the emergence of synthetic dyes, It is still used as sealing wax by the India Post but its use is being phased out.
Lac is used in folk medicine as a hepatoprotective and anti-obesity drug. It is used as a varnish for musical instruments such as violins and is soluble in alcohol. This type of lac was used in the finishing of 18th-century fowling guns in the United States.
Production levels
thumb|Processed shellac flakes from lac insect resin.
India exported significant amounts of sticklac derivatives, especially lac dye, from the 1700s to the late 1800s. Production declined as synthetic dyes emerged, and after the late 1940s, production of seedlac and shellac also declined due to replacement.